The present disclosure relates generally to hybrid vehicles such as off-highway vehicles (OHV), locomotives, trolley systems, and the like, and, more particularly, to hybrid vehicle power control systems and methods.
Off-highway (OHV) vehicles, including trolley connected OHVs and other large traction vehicles, are commonly powered by electric traction motors coupled in driving relationship to one or more axles or motor-wheel sets of the vehicle. In the motoring or traction mode of operation, the traction motors are supplied with electric current from a controllable source of electric power (e.g., an engine-driven traction alternator/rectifier/inverter combination or, alternatively, a direct current drive source including a dc motor without an inverter) and apply torque to the vehicle wheels which exert tangential force or tractive effort on the surface on which the vehicle is traveling (e.g., a haulage track or road), thereby propelling the vehicle in a desired direction along the right of way.
Conversely, in an electrical (i.e., dynamic) braking mode of operation, the same motors serve as axle-driven electrical generators. Torque is applied to the motor shafts by their respectively associated axle-wheel sets which then exert braking effort on the surface, thereby retarding or slowing the vehicle's progress. Because there is no suitable storage medium for the resulting generated electrical energy in a conventional off-highway vehicle or trolley, an electrically resistive grid (known as a dynamic braking grid or load box) is used to convert the electrical energy into heat energy, which is then vented to the atmosphere.
In contrast, hybrid OHVs and hybrid trolley OHVs have the capability of storing the generated dynamic braking energy in a suitable storage element(s) such as batteries, flywheels, ultracapacitors and the like. This stored energy may then be used for traction and/or auxiliary systems in the OHV, thereby improving fuel efficiency. Because these associated power storage elements are now added to the power system in an OHV, it would be desirable to obtain further secondary benefits therefrom such as, for example, reducing the stress on power components, improving the fuel efficiency by optimizing the system operating voltages, and attaining better dynamic operation of the vehicle, among other aspects.